Starting requires four things, fuel, spark, air, and compression. A starting problem is almost never lack of air or compression so focus on the first two. Did you turn on the petcock? Check for spark by pulling a plug, attaching it to its boot, grounding a metal side part or thread of the plug to the engine, and trying to start the bike. Make sure you are in neutral for this. Do this in a darker garage not in sunlight and you should see the spark. Try this for all four plugs.